Reprocessing of dialyzers is often performed with nonsterile solutions
possibly contaminated with bacterial-derived cytokine-inducing substa
nces. We investigated the retention of cytokine-inducing substances in
side the dialyzer during reprocessing in a closed loop in vitro hemodi
alysis system using a polyamide high flux membrane. After the first in
vitro circulation of human whole blood, rinse of the blood compartmen
t (BC) and reverse ultrafiltration (RUF) was performed with either cyt
okine-inducing substance-free saline or saline contaminated with filtr
ates from Pseudomonas cultures (6 ng/ml LAL-reactive material); subseq
uently, dialyzers were stored in 2% formaldehyde. Dialyzers were rinse
d with approximately 15 liters pyrogen-free saline before the second c
irculation using blood from the same donor; the effluates were free of
cytokine-inducing substances and formaldehyde. Before and after the b
lood circulations, peripheral blood mononuclear cells (PBMC) were sepa
rated and total production of IL-1 alpha and IL-1 beta was determined
after overnight incubation. In noncirculated PBMC as well as in PBMC s
eparated after whole blood circulation with pyrogen-free processed dia
lyzers, production of IL-1 beta was not detectable. After contaminated
rinse of the BC, production of IL-1 beta could be observed (1,600 +/-
1,100 pg/ml, mean +/- SEM). When pyrogen-free RUF was performed after
contaminated BC rinse, IL-1 beta production averaged 163 +/- 92 pg/ml
when using reused dialyzers, but 1,820 +/- 880 pg/ml when using new d
ialyzers. After reuse with pyrogen-free BC-rinse and contaminated RUF
no IL-1 beta synthesis was observed; however, when pyrogen-free BC-rin
se and contaminated RUF was applied to new dialyzers, IL-1 beta synthe
sis averaged 1,620 +/- 1,200 pg/ml. We conclude that cytokine-inducing
substances are retained inside the dialyzer, probably by adsorption t
o the membrane as well as to the protein layer covering the membrane a
nd are still biologically active after sterilisation. Cytokine-inducin
g substances substances are retained inside the dialyzer, probably by
adsorption to the membrane as well as to the protein layer covering th
e membrane and are still biologically active after sterilisation. Cyto
kine-inducing substances adsorbed to the protein layer can be partiall
y removed by RUF. Finally, the protein layer on the membrane appears t
o reduce the convective transfer of cytokine-inducing substances from
the dialysate into the blood compartment.